Common-mode plasmon sensing scheme as a high-sensitivity compact SPR sensor

A deep metal grating enables quasi-phase-matched simulta-neous excitation of two counterpropagating surface plasmon modes by means of its +1st and -2nd diffraction orders. The resulting angular reflection spectra of the scattered -1st and zeroth orders exhibit three interleaved zeros and maxima in a range centered around the Littrow angle. The spec-tra differ thoroughly from the usual reflection dip resulting from single-order plasmon coupling that produces strong absorption. The zeroth and -1st orders exhibit two cross-ing angles enabling high-sensitivity common-mode detection schemes designed to reject variations in source power and environmental noise. The proof of concept and experimen-tal assessment of this new surface plasmon resonance (SPR) sensing scheme are demonstrated by monitoring gases in a pressure-controlled chamber. A limit of detection (LOD) of 2 x 10-7 refractive index unit (RIU) was achieved. & COPY; 2023 Optica Publishing Group

Automated summary

A deep metal grating allows for simultaneous excitation of two counterpropagating surface plasmon modes using diffraction orders. The resulting angular reflection spectra exhibit three interleaved zeros and maxima. This new surface plasmon resonance sensing scheme shows high sensitivity and a limit of detection of 2 x 10-7 refractive index unit (RIU) was achieved.